Heat exchanger tube and heat exchanger employing the same

ABSTRACT

In a compact heat exchanger, a heat exchanger tube adapted for precision assembly of an outer tube and an inner tube and free from decreasing heat transfer efficiency is provided. For this purpose, the heat exchanger tube includes: a plurality of parallel outer tubes; inner tubes inserted in the outer tubes and having their opposite ends extended outward of the outer tubes; a gap support member formed of a wire material disposed in a gap between an inner periphery of the outer tube and an outer periphery of the inner tube and making spiral contact with the inner periphery and the outer periphery substantially throughout the length of the outer tube; and a supporting member making spiral contact with an inner periphery of the inner tube throughout the length of the inner tube.

TECHNICAL FIELD

The invention relates to a heat exchanger tube and a heat exchanger employing the same such as a multi-tube heat exchanger.

BACKGROUND ART

As the multi-tube heat exchanger, a double-tube heat exchanger is known in which an inner tube is inserted through an outer tube such that heat exchange is performed between fluid flowing through the inner tube and fluid flowing through space between the inner tube and the outer tube. This heat exchanger is applied to a heat pump water heater, heating unit or the like which uses a refrigerant. The heat pump water heater or the like supplies hot water by heating water flowing through space between the inner tube and the outer tube with a high-pressure and high-temperature refrigerant fluid flowing through the inner tube.

In order to obtain a predetermined hot water supply capacity, this double-tube heat exchanger has a long double-tube structure with increased heat transfer area. Hence, this heat exchanger needs to be bent or coiled into a predetermined outside configuration such as to be assembled in an apparatus. This leads to difficulty in downsizing. Further, the heat exchanger has to employ a tube member having a large diameter because the pressure loss of the fluid (refrigerant, water) increases with the increase in the total length of the structure. Namely, the heat exchanger cannot employ a small-diameter tube having excellent pressure resistance to the high-pressure refrigerant. As a solution to the above problems, the following Patent Literature 1 discloses a structure where a plurality of double-tubes having the inner tubes inserted through the outer tubes are arranged in parallel, ends of the outer tubes are connected to an inner header tube for communication of the outer tubes, the inner tubes extended through the inner header tube are connected to an outer header tube for communication thereof. This structure notably reduces the pressure loss of the fluid to provide for the use of the small-diameter tube and is made compact to be easily assembled into the apparatus.

CITATION LIST Patent Literature

-   Patent Literature 1: JP-A No. 2005-127684

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

While employing the inner tube and outer tube having small diameters to realize the compact design, the above-described conventional double-tube heat exchanger has to be constructed to ensure the flow of the fluid through a gap between the outer tube and the inner tube for the sake of heat transfer. The joint parts between the outer tubes, inner tubes and header tubes have to be made with precisions. Such tube members are generally joined together by brazing. In some cases, a brazing material may overflow due to the heat during brazing. Leakage of the brazing material to the outside can be visually inspected but the double-tube structure makes it impossible to visually inspect the leakage of the brazing material into the tube. If the brazing material leaks into the gap between the inner tube and the outer tube, the flow passage is blocked or the sectional area of the flow passage varies so that sufficient heat transfer efficiency cannot be achieved.

In the double-tube heat exchanger of Patent Literature 1, the center of the inner tube defines a straight space where the flow of heat medium has small resistance but a large amount of heat medium flows without contacting the inner tube. Hence, the heat exchanger fails to accomplish efficient heat exchange.

In view of the above, the invention has been accomplished and has objects to fabricate a heat exchanger tube for use in a compact heat exchanger that permits the outer tube and the inner tube to be assembled with high precisions and does not induce a decrease in the heat transfer efficiency, and to provide a heat exchanger tube capable of increasing the efficiency of heat exchange between the inner tube and the heat medium as well as a heat exchanger employing the heat exchanger tube.

Means for Solving the Problems

Next, means for solving the above problems is described with reference to drawings corresponding to embodiments of the invention.

A heat exchanger tube 11 according to a first aspect of the invention includes: an outer tube 13;

an inner tube 15 inserted in the outer tube 13;

a gap support member 17 including a wire material which is disposed in a gap W between an inner periphery of the outer tube 13 and an outer periphery of the inner tube 15, and makes spiral contact with the inner periphery and the outer periphery substantially throughout the length of the outer tube 13; and

a supporting member 19 including a wire material which makes spiral contact with an inner periphery of the inner tube 15 throughout the length of the inner tube 15.

This heat exchanger tube 11 has a structure where the inner tube 15 defining a primary flow passage is supported from inside by the supporting member 19, and the inner tube 15 and the outer tube 13 are supported by the gap support member 17. This gap support member 17 positions a secondary flow passage defining a pipe-shaped gap having an annular cross section, and accounts for the same gap along the circumference of the flow passage. This increases alignment precision of the outer tube 13 and the inner tube 15 in assembly and simplifies an assembly procedure. Further, the gap support member prevents the outer tube 13 and the inner tube 13 from being displaced and hence, the flow passage is fixed in terms of the sectional area and is not decreased in heat transfer efficiency.

A heat exchanger tube 11 according to a second aspect of the invention is the heat transfer tube 11 of the first aspect thereof which has a characteristic that the gap support member 17 is formed of a coil material and has a wire diameter d1 substantially equal to the gap W.

In this heat exchanger tube 11, the gap support member 17 formed of the coil material permits the outer tube 13 and the inner tube 15 to be easily assembled together with a constant gap maintained therebetween and to define the flow passage in the constant gap therebetween. Further, the gap support member 17 is interposed in the gap for the sake of heat transfer, providing a large heat transfer area.

A heat exchanger tube 11 according to a third aspect of the invention is the heat exchanger tube 11 of the first aspect thereof which has a characteristic that the gap support member 45 is formed of a coil material having a small diameter portion 43 and a large diameter portion 41 alternately formed, and has a wire diameter d1 smaller than the gap W, a coil inside diameter D1 at the small diameter portion 43 defined by an outside diameter D5 of the inner tube 15, and a coil outside diameter D2 at the large diameter portion 41 defined by an inside diameter D4 of the outer tube 13, thus supporting the inner tube 15 in the outer tube 13.

In this heat exchanger tube 11, the small diameter portion 43 of the gap support member 45 supports the inner tube 15 while the large diameter portion 41 supports the outer tube 13 on the inner periphery thereof. Since the wire diameter d1 of the gap support member 45 and a clearance 47 exist in the gap W between the outer periphery of the inner tube 15 and the inner periphery of the outer tube 13, a sufficient flow passage area can be obtained.

A heat exchanger tube 11 according to a fourth aspect of the invention includes: an outer tube 13;

an inner tube 15 inserted in the outer tube 13;

a gap support member 17 formed of a wire material which is disposed in a gap 31 between an outer-tube inner peripheral surface 32 and an inner-tube outer peripheral surface 30, and makes spiral contact with the outer-tube inner peripheral surface 32 and the inner-tube outer peripheral surface 30 substantially throughout the length of the outer tube 13;

a supporting member 19 formed of a wire material which makes spiral contact with a inner-tube inner peripheral surface 38 throughout the length of the inner tube 15; and

a heat transfer member 20 which is extended centrally through the supporting member 19 throughout the length of the supporting member 19 and at least a part of the outer periphery of the heat transfer member 20 is in contact with the supporting member 19.

In this heat exchanger tube 11, the heat medium flows through the inner tube 15 as making contact with the heat transfer member 20 disposed inside the inner tube 15 and with the supporting member 19 so that resistance is applied to a flow of the heat medium through the inner tube 15, thus producing a meandering flow of heat medium. The heat medium is increased in contact area as compared with a conventional state where the heat medium flows straight through the inner tube 15 so that only the heat medium close to the inner-tube inner peripheral surface 38 is subjected to heat exchange with the inner tube 15. The heat medium is brought into contact the heat transfer member 20, the supporting member 19 and the inner-tube inner peripheral surface 38 by coming into contact with the heat transfer member 20, and performs heat exchange by transferring heat to these heat transfer member 20, supporting member 19 and inner tube 15. The exchanged amount of heat is thermally conducted to the inner-tube outer peripheral surface 30 and subjected to heat exchange with a heat medium of another system that flows through the gap 31 between the outer tube 13 and the inner tube 15. Namely, the amount of heat exchanged with the heat transfer member 20 contributes to an additional increase in heat exchange efficiency.

A heat exchanger tube 11 according to a fifth aspect of the invention is the heat exchanger tube 11 of the fourth aspect thereof which has a characteristic that the heat transfer member 20 is a sheet 141 elongated in a longitudinal direction of the supporting member 19 and twisted spirally.

In this heat exchanger tube 11, the sheet 141 is spirally extended as contacting the supporting member 19 so that the heat medium flowing through the inner tube 15 moves through the inner tube 15 as spirally rotating. Thus, the heat medium contacting the heat transfer member 20 is increased in the contact area and contact time as compared with the case where the heat medium flows in parallel to the axis.

A heat exchanger tube 11 according to a sixth aspect of the invention is the heat exchanger tube 11 of the fourth aspect thereof which has a characteristic that the heat transfer member 20 is an outer-periphery protruding round rod 153 including oval portions 155 made by deforming a round outer periphery thereof at predetermined space intervals in the longitudinal direction of the supporting member 19.

In this heat exchanger tube 11, the round rod material is deformed in a manner to be clamped in a direction perpendicular to the axis so that a clamped portion protrudes radially outwardly to define the oval portion 155. This oval portion 155 is configured to make contact with the supporting member 19 at protruded tips thereof. The flow passage of the heat medium can be stirred and made to meander by alternately changing the clamping direction by 90°, for example.

A heat exchanger tube 11 according to a seventh aspect of the invention is the heat exchanger tube 11 of the fourth aspect thereof which has a characteristic that the heat transfer member 20 is a different-diameter round rod 161 with its round outer periphery alternately formed of a small diameter portion 159 and a large diameter portion 157 at predetermined space intervals in the longitudinal direction of the supporting member 19.

In this heat exchanger tube 11, the different-diameter round rod 161 is inserted in the inner tube 15 so that the heat medium flowing along the different-diameter round rod 161 moves as colliding against the large diameter portions 157. This collision disturbs the flow of heat medium, reducing the heat medium passing through without contacting the inner-tube inner peripheral surface 38 or the heat transfer member 20.

A heat transfer tube 11 according to an eighth aspect of the invention is the heat exchanger tube 11 of the fourth aspect thereof which has a characteristic that the heat transfer member 20 a solid rod 165 having a polygonal cross section.

In this heat exchanger tube 11, the heat transfer member 20 having a triangular cross section, for example, can provide a plurality of contact places with the heat medium in contrast to the sheet 141 allowing contact with the heat medium mainly on the front and back sides thereof. Particularly, a heat transfer member having a star-like cross section can further increase the contact area without reducing the flow passage.

A heat exchanger 49 according a ninth aspect of the invention is a heat exchanger 49 employing the heat transfer tube 11 according to any one of the first to eighth aspects thereof which has a characteristic that a plurality of the heat exchanger tubes 11 are arranged in mutually parallel relation,

a primary flow passage is formed by connecting all the inner-tube inlet ends to a primary branch tube 21 and connecting all the inner-tube outlet ends to a primary collecting tube 27, and

a secondary flow passage is formed by connecting all the outer-tube inlet ends to a secondary branch tube 25 and connecting all the outer-tube outlet ends to a secondary collecting tube 29.

In this heat exchanger 49, the plural heat transfer tubes 11 are arranged parallel to one another and in adjacency relation on one plane where the outer tubes 13 and the inner tubes 15 are laid out. This heat exchanger 49 constructed on one plane is used one unit such that the units can be stacked in plural layers to build a structure reduced in the ground contact area but increased in the heat transfer area.

In the heat exchanger 49 equipped with the heat transfer member 20, the heat medium flows through the inner tube 15 as contacting the heat transfer member 20 disposed inside the inner tube 15 and hence, the contact area of the heat medium, which is conventionally in contact only with the inner-tube inner peripheral surface 38, is increased. By contact with the heat transfer member 20, the heat medium performs heat exchange with the heat transfer member 20 through heat conduction. The exchanged amount of heat is thermally conducted to the inner tube 15 and subjected to heat exchange with the heat medium of another system that flows through the gap 31 between the outer tube 13 and the inner tube 15. Namely, the amount of heat exchanged with the heat transfer member 20 contributes to an additional increase in heat exchange efficiency. Further in this heat exchanger 49, the plurality of heat exchanger tubes 11 composed of the outer tubes 13 and the inner tubes 15 are arranged parallel to one another and in adjacency relation on one plane. This heat exchanger 49 constructed on one plane is used as one unit such that the plural units can be stacked in plural layers to build a structure reduced in the ground contact area but increased in the heat transfer area.

A heat exchanger 65 according to a tenth aspect of the invention is a heat exchanger employing the heat exchanger tube 11 according to any one of the first to eighth aspects thereof which has a characteristic that the plurality of heat exchanger tubes 11 are bundled, the bundle of heat exchanger tubes 11 is housed in a cylindrical shell 67, a primary flow passage is formed by interconnecting inlet ends of the inner tubes 15 and interconnecting outlet ends of the inner tubes 15, a secondary flow passage is formed by interconnecting inlet ends of the outer tubes 13 and interconnecting outlet ends of the outer tubes 13, and an interior of the shell 67 is configured as a tertiary flow passage.

In this heat exchanger 65, the plural bundled heat exchanger tubes 11 permit heat exchange between their respective outer tubes 13 and inner tubes 15 in the shell 67 and also permits heat exchange with the heat medium flowing through the shell 67.

A heat exchanger 65 according to an eleventh aspect of the invention is the heat exchanger 65 according to the tenth aspect thereof which has a characteristic that a plurality of straightening plates 87 having planes perpendicular to a longitudinal direction of the heat exchanger tubes 11 are disposed in the shell 67 so as to support the individual heat exchanger tubes 11 and to make the tertiary flow passage meander.

In this heat exchanger 65, the heat medium flowing through the shell 67 is made to meander by the straightening plates 87 or flows in a direction substantially perpendicular to the longitudinal direction of the heat exchanger tubes 11 in the shell 67 as forming the long tertiary flow passage. The heat medium performs heat exchange with the outer tubes 13 of the heat exchanger tubes 11 via the increased heat transfer area.

Effects of the Invention

According to the heat exchanger tube of the first aspect of the invention, the inner tube and the outer tube are supported by the gap support member, which positions the secondary flow passage defining the pipe-shaped gap having the annular cross section and accounts for the same gap along the circumference of the flow passage. This increases the alignment precision of the outer tube and the inner tube being assembled and simplifies the assembly procedure. By possessing the gap support member and the supporting member, the heat exchanger tube does not suffer displacement between the inner tube and the outer tube. When brazed, the inner tube and the outer tube can be fixedly brazed to their respective positions without suffering deviation of the brazing filler metal or leakage thereof. Because of the structure where the gap support member and the supporting member support the inner tube wall and the outer tube wall, these inner tube and outer tube can be reduced in wall thickness, which results in a further increase in thermal conductivity. This also makes it possible to further downsize the heat exchanger. In addition, the outer tube and inner tube are concentrically positioned without deviation so that the flow passage is fixed in terms of the sectional area and is not decreased in heat transfer efficiency. Since the flow passage is spirally formed, the fluid in the tubes flows smoothly in a tube axial direction, evenly transferring heat to the enter tube walls. Further, the gap support member and supporting member serve as a heat transfer body, further increasing the heat transfer efficiency.

According to heat exchanger tube of the second aspect, the heat exchanger tube is constructed using the gap support member formed of the wire material so that the outer tube and the inner tube with the constant gap maintained therebetween can be easily assembled together. Namely, the gap support member serves as a guide in inserting or fitting the inner tube in or with the outer tube, providing easy assembly work and high precision assembly. Further, the gap support member can provide the flow passage in the constant gap.

According to the heat exchanger tube of the third aspect, the small diameter portion of the gap support member supports the inner tube while the large diameter portion thereof supports the outer tube on the inner peripheral surface. Since the wire diameter of the gap support member and the clearance exist in the gap portion between the outer periphery of the inner tube and the inner periphery of the outer tube, a sufficient flow passage area can be obtained.

According to the heat exchanger tube of the fourth aspect of the invention, the inner tube and the outer tube are supported by the gap support member, which positions the secondary flow passage defining the pipe-shaped gap having the annular cross section and accounts for the same gap along the circumference of the flow passage. This increases the alignment precision of the outer tube and the inner tube being assembled and simplifies the assembly procedure. By possessing the gap support member and the supporting member, the heat exchanger tube does not suffer displacement between the inner tube and the outer tube. When brazed, the inner tube and the outer tube can be fixedly brazed to their respective positions without suffering deviation of the brazing filler metal or leakage thereof. Because of the structure where the gap support member and the supporting member support the inner tube wall and the outer tube wall, these inner tube and outer tube can be reduced in wall thickness, which results in a further increase in thermal conductivity. This also makes it possible to further downsize the heat exchanger. In addition, the heat transfer member supports the supporting member, bringing the supporting member into intimate contact with the inner tube. The outer tube and inner tube are concentrically positioned without deviation so that the flow passage is fixed in terms of the sectional area and is not decreased in heat transfer efficiency. Since the flow passage is spirally formed by the gap support member and the supporting member while the heat transfer member causes the flow to meander, the fluid flow in the tubes in the tube axial direction makes sufficient contact with the tubes, evenly transferring heat to the enter tube walls. Further, the gap support member, the supporting member and the heat transfer member each serve as a heat transfer body, further increasing the heat transfer efficiency.

According to the heat exchanger tube of the fifth aspect of the invention, the sheet formed of a low-cost material and twisted spirally is used to bring the heat medium in the inner tube into spiral rotation with a relatively small increase in flow loss whereby the efficiency of heat exchange between the inner tube and the heat medium flowing therethrough can be increased.

According to the heat exchanger tube of the sixth aspect of the invention, the oval portion protruded radially outwardly contacts the supporting member at the protruded end thereof. This oval portion can stir and cause meandering of the flow passage of the heat-medium, thus increasing heat exchange efficiency of the heat medium flowing through the inner tube.

According to the heat exchanger tube of the seventh aspect of the invention, the heat medium flowing through the inner tube is stirred by the large diameter portions and the small diameter portions of the different-diameter round rod. This facilitates the contact of the heat medium with the inner tube and the heat transfer member and increases heat exchange efficiency.

According to the heat exchanger tube of the eighth aspect of the invention, the efficiency of heat exchange between the heat medium and the heat transfer member and supporting member can be increased by increasing the surface area of the heat transfer member.

According to the heat exchanger of the ninth aspect of the invention, the plural heat exchanger tubes of a predetermined length are arranged on the same plane so as to increase the heat transfer area for the primary heat medium and the secondary heat medium in the limited installation area. Thus, a space-saving heat exchanger having high temperature effectiveness can be obtained. This plate-like heat exchanger is used as a unit such that the plural units can be stacked in plural layers, increasing the efficiency of heat exchange between the inner tube and the heat medium flowing therethrough. A compact, high-efficiency heat exchanger can be constructed on a small installation area.

According to the heat exchanger of the tenth aspect of the invention, the inner tube and the outer tube can be positioned relative to each other with high precisions by virtue of the gap support member and the supporting member. If the individual tubes are bundled together, the primary flow passage and the secondary flow passage are formed uniformly. The plural bundled heat exchanger tubes are arranged in the cylindrical shell to provide reliable heat exchange by three types of heat media in the inner tubes, the outer tubes and the shell.

According to the heat exchanger of the eleventh aspect of the invention, the heat medium flowing through the shell is made to meander by the straightening plates disposed in the shell, increasing the heat transfer area for the heat exchanger tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a schematic enlarged sectional view of a heat exchanger tube according to the invention, FIG. 1( b) showing a sectional view thereof taken on the line A-A in FIG. 1( a).

FIG. 2( a) is a plan view of a heat-exchanger tube array unit including the heat exchanger tubes according to the invention, FIG. 2( b) showing a sectional view thereof taken on the line B-B in the plan view.

FIG. 3 is a sectional side elevation of the heat-exchanger tube array unit taken on the line C-C in FIG. 2.

FIG. 4 is a fragmentary enlarged sectional view of the sectional view shown in FIG. 2( b).

FIG. 5 is a sectional view of a heat exchanger tube according to another embodiment of the invention.

FIG. 6( a) is a schematic enlarged sectional view of a heat exchanger tube according to the invention, FIG. 6( b) showing a sectional view thereof taken on the line A-A in FIG. 6( a).

FIG. 7( a) is a plan view of a heat-exchanger tube array unit including the heat exchanger tubes according to the invention, FIG. 7( b) showing a sectional view of a plane perpendicular to a primary branch tube and including the axis of the inner tube.

FIG. 8 is a front view of the outer tubes and inner tubes as seen from the inside of a secondary branch tube.

FIG. 9 is an enlarged view of an essential part of FIG. 7B.

FIG. 10( a) is a sectional view of a heat exchanger tube including a heat transfer member formed by twisting a sheet through 90° at a predetermined length interval, FIG. 10( b) showing a sectional view thereof taken on the line B-B in FIG. 10( a), FIG. 10( c) showing a sectional view thereof taken on the line C-C in FIG. 10( a).

FIG. 11 is a perspective view of the heat transfer member shown in FIG. 10.

FIG. 12 is a perspective view of an outer-periphery protruding round rod including outer peripheral portions deformed into an oval shape and turned around 90° at predetermined-length intervals.

FIG. 13( a) is a sectional view of a heat exchanger tube including the outer-periphery protruding round rod shown in FIG. 12, FIG. 13( b) showing a sectional view thereof taken on the line D-D in FIG. 13( a), FIG. 13( c) showing a sectional view thereof taken on the line E-E in FIG. 13( a), FIG. 13( d) showing a sectional view thereof taken on the line F-F in FIG. 13( a).

FIG. 14( a) is a sectional view of a heat exchanger tube including a different-diameter round rod having a large diameter portion and a small diameter portion alternately formed, FIG. 14( b) showing a sectional view thereof taken on the line G-G in FIG. 14( a), FIG. 14( c) showing a sectional view thereof taken on the line H-H in FIG. 14( a).

FIG. 15( a) is a sectional view of a heat exchanger tube including a constricted round rod having large diameter portions and small diameter portions defined by a smooth surface, FIG. 15( b) showing a sectional view thereof taken on the line I-I in FIG. 15( a), FIG. 15( c) showing a sectional view thereof taken on the line J-J in FIG. 15( a).

FIG. 16( a) is a sectional view of a heat exchanger tube including a solid rod having a polygonal cross section, FIG. 16( b) showing a sectional view thereof taken on the line K-K in FIG. 16( a).

FIG. 17 is a sectional view of a heat exchanger tube including a heat transfer member of the round rod type according to each of the above configuration examples, the heat transfer member having a stream-lined end.

FIG. 18 is a perspective view of a heat exchanger constructed using the heat exchanger tubes according to the invention.

FIG. 19 is a schematic exploded perspective view of a heat exchanger according to another embodiment constructed using the heat exchanger tubes according to the invention.

FIG. 20 is a sectional side elevation of the heat exchanger shown in FIG. 19.

BEST MODES FOR CARRYING OUT THE INVENTION

A first embodiment of the invention is first described with reference to the accompanying drawings.

FIG. 1( a) is a schematic enlarged sectional view of a heat exchanger tube according to the invention and FIG. 1( b) is a sectional view thereof taken on the line A-A in FIG. 1( a). FIG. 2( a) is a plan view of a heat-exchanger tube array unit including the heat exchanger tubes according to the invention and FIG. 2( b) is a sectional view thereof taken on the line B-B in the above plan view. FIG. 3 is a sectional side elevation of the heat-exchanger tube array unit taken on the line C-C in FIG. 2. FIG. 4 is a fragmentary enlarged sectional view of the cross section shown in FIG. 2( b).

A heat exchanger tube 11 according to this embodiment includes an outer tube 13, an inner tube 15, a gap support member 17 and a supporting member 19.

The outer tube 13 is formed of a straight thin tube. The inner tube 15 is inserted in the outer tube 13 and has opposite ends extended outward of the opposite ends of the outer tube 13. The inner tube 15 and the outer tube 13 are in concentric relation.

The plural heat exchanger tubes 11 are arranged in parallel and adjacent relation so as to form one plane, or arranged into a rectangular tube array to form a heat-exchanger tube array unit that constitutes a heat exchanger.

Inlet ends of all the inner tubes 15 arranged in parallel are connected to a primary branch tube 21, one end of which is closed with a plug 23. Inlet ends of all the outer tubes 13 are connected to a secondary branch tube 25. The secondary branch tube 25 has one end closed with the plug 23 and is penetrated by the above inner tubes 15. Outlet ends of all the inner tubes 15 are connected to a primary collecting tube 27, the other end of which is closed with the plug 23. Outlet ends of all the outer tubes 13 are connected to a secondary collecting tube 29, the other end of which is closed with the plug 23. The secondary collecting tube 29 is penetrated by the inner tubes 15. According to the embodiment, the primary branch tube 21, the primary collecting tube 27, the secondary branch tube 25 and the secondary collecting tube 29 are each formed of a straight round pipe.

A gap 31 forming a flow passage is defined between an outer periphery of the inner tube 15 and an inner periphery of the outer tube 13. The gap support member 17 is interposed in this gap portion. The gap support member 17 is a coil material having a wire diameter d1 substantially equal to a gap length (gap width) W between the inner periphery of the outer tube 13 and the outer periphery of the inner tube 15. Specifically, the gap support member 17 formed of the coil material has a coil inside diameter D1 equal to an outside diameter D5 of the inner tube 15 (D1=D5) and a coil outside diameter D2 equal to an inside diameter D4 of the outer tube 13 (D2=D4). The gap support member makes spiral contact with the inner periphery of the outer tube 13 and the outer periphery of the inner tube 15 and spaces the outer tube 13 and the inner tube 15 apart by the gap W (d1=W=(D4−D5)/2) equal to the wire diameter d1. Thus, the gap support member supports the inner tube 15 and the outer tube 13 substantially throughout the length of the outer tube 13.

The inner tube 15 is provided with the supporting member 19 which is in contact with the inner periphery thereof. The supporting member 19 is formed of a coil material having a wire diameter d2 substantially equal to that of the gap support member 17 and a coil outside diameter D3 equal to an inside diameter D6 of the inner tube 15. The supporting member is adapted to support the inner tube 15 from inside by making spiral contact with the inner periphery of the inner tube 15.

As shown in FIG. 4, the outer tube 13 is inserted in the secondary collecting tube 29 through an outer-tube insertion hole 33 drilled through a tube wall of the secondary collecting tube 29 on one side thereof and opens into the inside of the secondary collecting tube 29. The secondary collecting tube 29 is formed with an inner-tube through-hole 35 drilled through the other side of the tube wall of the secondary collecting tube 29. The inner tube 15 penetrating the inner-tube through-hole 35 is inserted through an inner-tube insertion hole 37 drilled through the primary branch tube 21 and opens into the inside of the primary branch tube 21.

The tubes at these through-hole portions are hermetically fixed to each other by brazing. The brazing may be performed using a method of so-called preplaced brazing in which a brazing filler metal such as silver solder or brass solder is placed on contact surfaces between the tubes and brazed in a furnace so as to integrally join the tubes. Further, in the furnace, the gap support member 17 and supporting member 19 supporting the inner tube 15 and the outer tube 13 are also brazed to the inner periphery of the outer tube 13, the outer periphery of the inner tube 15 and the inner periphery of the inner tube 15 with the brazing filler metal, respectively. These gap support member 17 and supporting member 19 are formed of the coil material or a wire-like member molded into a spiral shape, such as a stainless steel coil material plated with copper, nickel or an alloy of these metals, or formed with a double plating layer of copper and nickel. The wire-like member has a wire diameter of 0.5 to 2 mm. In the furnace, the plating material serves as the brazing filler metal to bond the individual coil materials (17, 19) to the inner periphery of the outer tube 13, the outer periphery of the inner tube 15 and the inner periphery of the inner tube 15 which are in contact with the coil materials. The stainless steel coil may be a previously hardened coil material having spring elasticity or an untreated coil material formed of a straight wire material molded into the spiral shape. The untreated coil material permitting low-cost molding is preferred. Since the coil material is heat treated in the furnace along with the outer tube 13 and the inner tube 15, as described above, it is preferred to use the coil material yet to be subjected to the hardening treatment.

Before placed in the furnace, the inner tube 15 and the outer tube 13 are spot-welded only at ends thereof and temporarily fixed to each other. Subsequently, these tubes are assembled with the gap support member 17 and the supporting member 19 and placed in the furnace whereby the respective support members 17, 19 and the inner tubes 15 and the outer tubes 13 as well as the outer tubes 13, the inner tubes 15, the branch tubes 21, 25 and the collecting tubes 27, 29 are bonded together.

As shown in FIG. 3, the outer tubes 13 open into the inside of the secondary branch tube 25 while the inner tubes 15 are inserted in the outer tubes 13, respectively. The inner tubes 15 extend outward of the outer tubes 13 in the secondary branch tube 25 are each extended through the secondary branch tube 25 and open into the inside of the primary collecting tube 27. The plural outer tubes 13 with the inner tubes 15 inserted therethrough, the secondary branch tube 25 and the secondary collecting tube 29 connected to the opposite ends of the outer tubes 13, and the primary branch tube 21 and the primary collecting tube 27 connected to the opposite ends of the inner tubes 15 form a heat-exchanger tube array unit 39, shown in FIG. 2( a), that forms a rectangular shape on one plane.

According to the embodiment, the heat exchanger tube 11 employs ultrathin round metal tubes as the inner tube 15 and the outer tube 13. A ratio S1:S2 between the area S1 of a primary flow passage through the inner tube 15 and the area S2 of a secondary flow passage through the outer tube 13 is in the range of 1:2 to 2:1. The inner tube 15 has an inside diameter of 2 to 6 mm, or more preferably 3 to 5 mm. The outer tube 13 has an inside diameter of 4 to 10 mm, or more preferably 5 to 8.5 mm. A thickness of the tubes is in the range of 0.15 to 0.35 mm.

For example, it is provided that the inner tube 15 employs an SUS tube having an outside diameter D5=4 mm and an inside diameter D6=3.6 mm, the outer tube 13 employs an SUS tube having an outside diameter of 6.6 mm and an inside diameter D4=6 mm, and the gap support member 17 and the supporting member 19 each employs a copper-plated stainless steel coil material having a wire diameter d1=d2=1 mm. According to the cross section (FIG. 1( b)) of the heat exchanger tube 11 shown in FIG. 1, the areas of the primary flow passage and the secondary flow passage are calculated based on these numerical values. The area S1 of the primary flow passage is about 9.17 mm² and the area S2 of the secondary flow passage is about 14.70 mm². A ratio between these areas is roughly 1:1.6.

It is preferred to set the ratio between the area S1 of the primary flow passage and the area S2 of the secondary flow passage to 1:1 by suitably changing the above-described respective diametrical dimensions of the inner tube 15 and the outer tube 13 and the respective numerical values of the gap support member 17 and the supporting member 19. Since the sectional areas of the flow passages also vary depending upon the numbers of coils or coil pitches of the gap support member 17 and the supporting member 19, which are formed of the coil materials, relative to the respective tubes 13, 15, these coil materials may also be changed in the configuration. Further, the thermal conductivity can be increased by setting the ratio of flow rates through the inner tube 15 and the outer tube 13 to 1:1.

While the above-described embodiment illustrates the example where the gap support member 17 is configured such that the coil material has the fixed coil inside diameter D1 and coil outside diameter D2, the invention is not limited to this. As shown in FIG. 5, for example, a coil material having a large diameter portion 41 and a small diameter portion 43 alternately formed may be employed. This gap support member 45 has a configuration where the wire diameter d1 is smaller than the gap W between the inner tube 15 and the outer tube 13, the coil inside diameter D1 at the small diameter portion 43 is equal to the outside diameter D5 of the inner tube 15, the coil outside diameter D2 at the large diameter portion 41 is equal to the inside diameter D4 of the outer tube 13, and the inner tube 15 is supported in the outer tube 13. This heat exchanger tube 11 is adapted to provide a sufficient flow passage area because the wire diameter d1 of the gap support member 17 and a clearance exist in the gap W between the outer periphery of the inner tube 15 and the inner periphery of the outer tube 13.

Next, a second embodiment of the invention is described with reference to the drawings.

FIG. 6( a) is a schematic enlarged sectional view of a heat exchanger tube according to the invention, FIG. 6( b) showing a sectional view thereof taken on the line A-A in FIG. 6( a). FIG. 7( a) is a plan view of a heat-exchanger tube array unit including the heat exchanger tubes according to the invention, FIG. 7( b) showing a sectional view of a plane perpendicular to the primary branch tube and including the axis of the inner tube. FIG. 8 is a front view of the outer tubes and inner tubes as seen from the inside of the secondary branch tube. FIG. 9 is an enlarged view of an essential part of FIG. 7( b).

The heat exchanger tube 11 according to this embodiment includes the outer tube 13, the inner tube 15, the gap support member 17, the supporting member 19 and a heat transfer member 20.

The outer tube 13 is formed of a straight thin tube. The inner tube 15 is inserted in the outer tube 13 and has opposite ends extended outward of the opposite ends of the outer tube 13. The inner tube 15 and the outer tube 13 are in concentric relation.

The plural heat exchanger tubes 11 are arranged in parallel and adjacent relation so as to form one plane, or arranged into a rectangular tube array to form a heat-exchanger tube array unit 39.

The inlet ends of all the inner tubes 15 arranged in parallel are connected to the primary branch tube 21, one end of which is closed with the plug 23. The inlet ends of all the outer tubes 13 are connected to the secondary branch tube 25. The secondary branch tube 25 has one end closed with the plug 23 and is penetrated by the above inner tubes 15. The outlet ends of all the inner tubes 15 are connected to the primary collecting tube 27, the other end of which is closed with the plug 23. The outlet ends of all the outer tubes 13 are connected to the secondary collecting tube 29. The secondary collecting tube 29 is closed with the plug 23 at the other end thereof and penetrated by the inner tubes 15. According to the embodiment, the primary branch tube 21, the primary collecting tube 27, the secondary branch tube 25 and the secondary collecting tube 29 are each formed of a straight round pipe.

As shown in FIG. 6( a), the gap 31 forming the flow passage exists between an inner-tube outer peripheral surface 30 and an outer-tube inner peripheral surface 32. The gap support member 17 is inserted in this gap portion. The gap support member 17 is the coil material having the wire diameter d1 substantially equal to the gap length (gap width) W between the inner periphery of the outer tube 13 and the outer periphery of the inner tube 15.

Specifically, the gap support member 17 formed of the coil material has the coil inside diameter D1 equal to the outside diameter D5 of the inner tube 15 (D1=D5) and the coil outside diameter D2 equal to the inside diameter D4 of the outer tube 13 (D2=D4). The gap support member makes spiral contact with the inner periphery of the outer tube 13 and the outer periphery of the inner tube 15 and spaces the outer tube 13 and the inner tube 15 apart by the gap W substantially equal to the wire diameter d1 (d1=W=(D4−D5)/2). Thus, the gap support member supports the inner tube 15 and the outer tube 13 substantially throughout the length of the outer tube 13.

The inner tube 15 is provided with the supporting member 19 which is in contact with the inner periphery thereof. The supporting member 19 is formed of the coil material having the wire diameter d2 substantially equal to that of the gap support member 17 and the coil outside diameter D3 equal to the inside diameter D6 of the inner tube 15. The supporting member is adapted to support the inner tube 15 from inside by making spiral contact with the inner periphery of the inner tube 15.

The supporting member 19 is centrally provided with the heat transfer member 20. The heat transfer member 20 is extended throughout the length of the supporting member 19, making contact with the supporting member 19 at least at a part of the outer periphery thereof. According to this embodiment, this heat transfer member 20 is a sheet 141 elongated in a longitudinal direction of the supporting member 19 and twisted spirally. A width of the sheet 141 is substantially equal to an inside diameter D7 of the supporting member 19.

The outer tube 13 is inserted in the secondary branch tube 25 and in the secondary collecting tube 29 through the outer-tube insertion hole 33 drilled through the tube wall of the secondary branch tube 25 on one side thereof and through the outer-tube insertion hole 33 drilled through the secondary collecting tube 29 on one side thereof, opening into the inside of the secondary branch tube 25 and of the secondary collecting tube 29. The inner-tube through-hole 35 is drilled through the tube wall of the secondary branch tube 25 on the other side thereof and the tube wall of the secondary collecting tube 29 on the other side thereof. The inner tube 15 penetrating the inner-tube through-hole 35 is inserted through the inner-tube insertion hole 37 drilled through the primary branch tube 21 or through the inner-tube insertion hole 37 drilled through the primary collecting tube 27, opening into the inside of the primary branch tube 21 and into the inside of the primary collecting tube 27.

The tubes at these through-hole portions are hermetically fixed to each other by brazing. The brazing may be performed using a method of so-called preplaced brazing in which a brazing filler metal such as silver solder or brass solder is placed on contact surfaces between the tubes and brazed in the furnace so as to integrally join the tubes. Further, in the furnace, the gap support member 17 and supporting member 19 which support the inner tube 15 and the outer tube 13 as well as the heat transfer member 20 are also brazed to the outer-tube inner peripheral surface 32, the inner-tube outer peripheral surface 30 and an inner-tube inner peripheral surface 38 with the brazing filler metal, respectively. The gap support member 17 and the supporting member 19 are formed of the coil material which is the wire-like member molded into the spiral shape, such as the stainless steel coil material plated with copper, nickel or an alloy of these metals, or formed with a double plating layer of copper and nickel. The wire-like member has a wire diameter of 0.5 to 2 mm. In the furnace, the plating material serves as the brazing filler metal to bond the gap support member 17 and the supporting member 19 to the outer-tube inner peripheral surface 32, the inner-tube outer peripheral surface 30, and the inner-tube inner peripheral surface 38 (see FIG. 6( a)) and the heat transfer member 20 which are in contact with the coil materials. The stainless steel coil may be the previously hardened coil material having spring elasticity or the untreated coil material formed of the straight wire material molded into the spiral shape. The untreated coil material permitting low-cost molding is preferred. Since the coil material is heat treated in the furnace along with the outer tube 13 and the inner tube 15, as described above, it is preferred to use the coil material yet to be subjected to the hardening treatment.

Before placed in the furnace, the inner tube 15 and the outer tube 13 can be spot-welded only at ends thereof and temporarily fixed to each other. Subsequently, the inner tube 15 and the outer tube 13 can be assembled with the gap support member 17, the supporting member 19 and the heat transfer member 20 and placed in the furnace. Thus, the connections are made between the inner tube 15 and the supporting member 19, the supporting member 19 and the heat transfer member 20, the inner tube 15, the gap support member 17 and the outer tube 13, the primary branch tube 21 and the inner tubes 15, the primary collecting tube 27 and the inner tubes 15, the secondary branch tube 25 and the outer tubes 13, and the secondary collecting tube 29 and the outer tubes 13.

As shown in FIG. 8, the outer tubes 13 open into the inside of the secondary branch tube 25 while the inner tubes 15 are inserted in the outer tubes 13, respectively. The inner tubes 15 extended outward of the outer tubes 13 in the second branch tube 25 are each extended through the secondary branch tube 25 and open into the inside of the primary collecting tube 27. The plural outer tubes 13 with the inner tubes 15 inserted therethrough, the secondary branch tube 25 and the secondary collecting tube 29 connected to the opposite ends of the outer tubes 13, and the primary branch tube 21 and the primary collecting tube 27 connected to the opposite ends of the inner tubes 15 form the heat-exchanger tube array unit 39, shown in FIG. 7( a), that forms a rectangular shape on one plane.

According to this embodiment, the heat exchanger tube 11 employs ultrathin round metal tubes as the inner tube 15 and the outer tube 13. The sectional area S1 of the primary flow passage in the inner tube 15 is expressed as (the inside-diametrical sectional area of the inner tube 15—the sectional area of the supporting member—the sectional area of the sheet). The sectional area S2 of the secondary flow passage in the outer tube 13 is expressed as (the inside-diametrical sectional area of the outer tube 13—the outside-diametrical sectional area of the inner tube—the sectional area of the gap support member). A ratio between the sectional area S1 of the primary flow passage and the sectional area S2 of the secondary flow passage is in the range of S1:S2=1:2 to 2:1. The inner tube 15 has an inside diameter of 2 to 6 mm, or more preferably 3 to 5 mm. The outer tube 13 has an inside diameter of 4 to 10 mm, or more preferably 5 to 8.5 mm. A thickness of the tubes is in the range of 0.15 to 0.35 mm.

For example, it is provided that the inner tube 15 employs an SUS tube having an outside diameter D5=4 mm and an inside diameter D6=3.6 mm, the outer tube 13 employs an SUS tube having an outside diameter of 6.6 mm and an inside diameter D4=6 mm, the gap support member 17 and the supporting member 19 each employ a copper-plated stainless steel coil material having a wire diameter d1=d2=1 mm, and the sheet 141 has a width of 1.6 mm and a thickness of 0.21 mm. According to the cross section (FIG. 6( b)) of the heat exchanger tube 11 shown in FIG. 6, the sectional area S1 of the primary flow passage and the sectional area S2 of the secondary flow passage are calculated based on these numerical values. The sectional area S1 of the primary flow passage is about 8.5 mm² and the sectional area S2 of the secondary flow passage is about 14.0 mm². A ratio between these sectional areas is roughly 1:1.65.

It is preferred to set the ratio between the sectional area S1 of the primary flow passage and the sectional area S2 of the secondary flow passage to 1:1 by suitably changing the above-described respective diametrical dimensions of the inner tube 15 and the outer tube 13 and the respective numerical values of the gap support member 17, the supporting member 19 and the sheet 141. Since the sectional areas also vary depending upon the numbers of coils or coil pitches of the gap support member 17 and the supporting member 19, which are formed of the coil materials, relative to the inner tube 15 and the outer tube 13, these coil materials may also be changed in the configuration. Further, the thermal conductivity can be increased by setting the ratio of flow rates through the inner tube 15 and the outer tube 13 to 1:1.

The action of the above heat exchanger tube 11 is described.

The heat medium flows through the inner tube 15 as contacting the heat transfer member 20 and the supporting member 19 disposed inside the inner tube 15 and hence, the contact area of the heat medium, which is conventionally in contact only with the inner-tube inner peripheral surface 38, is increased. The heat medium exchanges heat with the heat transfer member 20 and the supporting member 19 by heat transfer through contact with the heat transfer member 20 and the supporting member 19. The exchanged amount of heat is thermally conducted to the inner tube 15 and subjected to heat exchange with the heat medium of another system that flows through the gap 31 between the outer tube 13 and the inner tube 15. Namely, the amount of heat exchanged in the inner tube 15 contributes to the additional increase in heat exchange efficiency.

The sheet 141 as the heat transfer member 20 is spirally inserted as contacting the supporting member 19, while the supporting member 19 is disposed in the inner tube 15 in a coiled form. Hence, the heat medium flows through the inner tube 15 as spirally rotating or meandering. This results in the increase in the contact area on which and the contact time in which the heat medium makes contact in the inner tube 15 as compared with a case where the heat medium forms a straight flow parallel to the axis. Hence, the efficiency of heat exchange between the inner tube 15 and the heat medium flowing therethrough can be increased using inexpensive materials and with a relatively small increase in flow loss.

FIG. 10( a) is a sectional view of a heat exchanger tube including a heat transfer member formed by twisting a sheet through 90° at a predetermined length interval, FIG. 10( b) showing a sectional view thereof taken on the line B-B in FIG. 10(a), FIG. 10( c) showing a sectional view thereof taken on the line C-C in FIG. 10( a). FIG. 11 is a perspective view of the heat transfer member shown in FIG. 10.

The heat transfer member 20 may be configured such that a rectangular sheet of a predetermined length is twisted into shorter spiral sheets 141 twisted through 180° at opposite ends which are turned through 90° at a predetermined length interval and interconnected at their ends. In this case, the sheets 141 can be inverted on a per-90° basis by forming slits 151 on the opposite ends of the width of the sheet with respect to the axis passing the widthwise center thereof. According to this configuration, the sheet 141 and the supporting member 19 located on an outer periphery of the sheet 141 jointly stir the heat medium in the inner tube 15 so as to increase the contact area of the heat medium. It is noted that the above-described twisting angle of 180° and turning angle of 90° of the sheet 141 are not limited to these. The sheet may be twisted through another twisting angle such as 90° or 120° or turned through another turning angle such as 45° or 60°.

FIG. 12 is a perspective view of an outer-periphery protruding round rod including outer peripheral portions deformed into an oval shape and turned around 90° at predetermined-length intervals. FIG. 13( a) is a sectional view of a heat exchanger tube including the outer-periphery protruding round rod shown in FIG. 12, FIG. 13( b) showing a sectional view thereof taken on the line D-D in FIG. 13( a), FIG. 13( c) showing a sectional view thereof taken on the line E-E in FIG. 13( a), FIG. 13( d) showing a sectional view thereof taken on the line F-F in FIG. 13( a).

The heat transfer member 20 is formed in an outer-periphery protruding round rod 153 including oval portions 155 made by deforming a round outer periphery thereof at predetermined space intervals in the longitudinal direction of the supporting member 19. A round rod material is deformed in a manner that a portion of the round rod is clamped in a direction perpendicular to the axis and the clamped portion protrudes radially outward to form the oval portion 155. This oval portion 155 is configured to make contact with the supporting member 19 at protruded tips thereof. The heat exchanger tube is adapted to stir and cause meandering of the flow passage of the heat medium by alternately changing this clamping direction by 90°, for example. It is provided, for example, that the inner tube 15 has an outside diameter D5=4.4 mm and an inside diameter D6=4.0 mm; the outer tube 13 has an outside diameter of 6.6 mm and an inside diameter D4=6 mm; the gap support member 17 has a wire diameter d1=0.8 mm; the supporting member 19 has a wire diameter d2=1 mm; and the outer-periphery protruding round rod 153 has a sectional area of 1.77 mm². According to the cross section (FIG. 13( b, c, d)) of the heat exchanger tube 11 shown in FIG. 13, the sectional area S1 of the primary flow passage and the sectional area S2 of the secondary flow passage are calculated based on these numerical values. The sectional area S1 of the primary flow passage is about 9.5 mm² and the sectional area S2 of the secondary flow passage is about 12.1 mm². A ratio between these sectional areas is roughly 1:1.27.

According to this heat transfer member 20, the outer-periphery protruding round rod 153 including the oval portions 155 adapted for heat conduction to the inner tube 15 can be fabricated at relatively low costs and with ease.

FIG. 14( a) is a sectional view of a heat exchanger tube including a different-diameter round rod having a large diameter portion and a small diameter portion alternately formed, FIG. 14( b) showing a sectional view thereof taken on the line G-G in FIG. 14( a), FIG. 14( c) showing a sectional view thereof taken on the line H-H in FIG. 14( a).

The heat transfer member 20 can be formed in a different-diameter round rod 161, a round outer periphery of which is defined by a small diameter portion 159 and a large diameter portion 157 alternately formed at predetermined space intervals in the longitudinal direction of the supporting member 19. A pitch of the supporting member 19 differs from a pitch between the large diameter portion 157 and the small diameter portion 159. For example, it is provided that the inner tube 15 has an outside diameter D5=4.0 mm and an inside diameter D6=3.6 mm, the outer tube 13 has an outside diameter of 6.6 mm and an inside diameter D4=6 mm, the gap support member 17 and the supporting member 19 each have a wire diameter d1=d2=1 mm, and the different-diameter round rod 161 has an outside diameter of 0.3 mm at the small diameter portion 159 and an outside diameter of 0.9 mm at the large diameter portion 157. According to the cross section (FIG. 14( b, c) of the heat exchanger tube 11 shown in FIG. 14, the sectional area S1 of the primary flow passage and the sectional area S2 of the secondary flow passage are calculated based on these numerical values. Ratios between these sectional areas are S1:S2≈1:1.7 at the large diameter portion 157 and S1:S2≈1:1.6 at the small diameter portion 159.

According to this heat transfer member 20, the insertion of the different-diameter round rod 161 in the inner tube 15 causes the heat medium flowing along the different-diameter round rod 161 to flow as colliding against the large diameter portions 157. This collision disturbs the flow of the heat medium and stirs the heat medium flowing through the inner tube 15, thus reducing the heat medium passing through the inner tube 15 without contacting the inner-tube inner peripheral surface 38, the supporting member 19 or the heat transfer member 20. The collision facilitates the contact of the heat medium with the inner tube 15, the supporting member 19 and the heat transfer member 20.

FIG. 15( a) is a sectional view of a heat exchanger tube including a constricted round rod having large diameter portions and small diameter portions defined by a smooth surface, FIG. 15( b) showing a sectional view thereof taken on the line I-I in FIG. 15( a), FIG. 15( c) showing a sectional view thereof taken on the line J-J in FIG. 15( a).

The heat transfer member 20 can be formed in a constricted round rod 163 having the large diameter portions 157 and the small diameter portions 159 defined by a smooth surface. For example, it is provided that the inner tube 15 has an outside diameter D5=4.4 mm and an inside diameter D6=4.0 mm, the outer tube 13 has an outside diameter of 6.6 mm and an inside diameter D4=6 mm, the gap support member 17 has a wire diameter d1=0.8 mm, the supporting member 19 has a wire diameter d2=1 mm, and the constricted round rod 163 has an outside diameter of 0.76 mm at the small diameter portion 159 and an outside diameter of 2.0 mm at the large diameter portion 157. According to the cross section (FIG. 15( b, c) of the heat exchanger tube 11 shown in FIG. 15, the sectional area S1 of the primary flow passage and the sectional area S2 of the secondary flow passage are calculated based on these numerical values. Ratios between these sectional areas are S1:S2≈1:1.47 at the large diameter portion 157 and S1:S2≈1:1.11 at the small diameter portion 159.

According to this heat transfer member 20, the heat medium flowing through the inner tube 15 is stirred and made to meander so that the contact of the heat medium with the inner tube 15, the supporting member 19 and the heat transfer member 20 is facilitated. By adopting the round rod material formed with a drawn part at a predetermined length interval, the large diameter portion 157 has substantially the same diameter as the inside diameter of the supporting member 19 so that the large diameter portion is also adapted to make contact with a part of the supporting member 19 and supporting the same.

FIG. 16( a) is a sectional view of a heat exchanger tube including a solid rod having a polygonal cross section, FIG. 16( b) showing a sectional view thereof taken on the line K-K in FIG. 16( a).

The heat transfer member 20 can be formed in a solid rod 165 having a polygonal cross section. According to the illustration, the heat transfer member is formed in the solid rod 165 having a substantially triangular cross section. The solid rod 165 is twisted so that the ridges thereof are substantially in spiral form or not in parallel to the axis.

For example, it is provided that the inner tube 15 has an outside diameter D5=4.4 mm and an inside diameter D6=4.0 mm, the outer tube 13 has an outside diameter of 6.6 mm and an inside diameter D4=6 mm, the gap support member 17 has a wire diameter d1=0.8 mm, the supporting member 19 has a wire diameter d2=1 mm, and the solid rod 165 has a sectional area of 1.8 mm². According to the cross section (FIG. 16( b)) of the heat exchanger tube 11 shown in FIG. 16, the sectional area S1 of the primary flow passage and the sectional area S2 of the secondary flow passage are calculated based on these numerical values. The sectional area S1 of the primary flow passage is about 9.5 mm² and the sectional area S2 of the secondary flow passage is about 12.1 mm². A ratio between these sectional areas is roughly 1:1.27.

In contrast to the above-described sheet 141 in contact with the heat medium mostly on the both sides thereof, this heat transfer member 20 can obtain plural contact positions with the heat medium by being configured to have the triangular cross section as in the illustration. Further, a flow toward the supporting member 19 is produced by virtue of the ridges substantially in the spiral form. Particularly, without reducing the flow passage (flow-passage sectional area), the contact area with the heat medium can be increased even further by forming a heat transfer member having a star-like cross section and spirally twisted similarly to the above. Thus, the surface area of the heat transfer member 20 is increased so as to increase the efficiency of heat exchange between the heat medium and the heat transfer member 20.

FIG. 17 is a sectional view of a heat exchanger tube including a heat transfer member of the round rod type according to each of the above configuration examples, the heat transfer member having a stream-lined end.

It is preferred that the heat transfer member 20 of the round rod type according to each of the above configuration examples has an end formed in a streamlined shape. The heat medium flow around the end of the heat transfer member 20 is reduced in separation from the surface thereof due to vortex and the like or in turbulence. The streamlined end of the heat transfer member provides smooth inflow and outflow of the heat medium and increases the heat transfer efficiency between the heat medium and the insides of the inner tube 15.

The heat exchanger tube 11 of this embodiment constitutes the heat-exchanger tube array unit 39, as described above, which may be constructed as a single unit. As shown in FIG. 18, a heat exchanger 49 may be constructed using a plurality of the heat-exchanger tube array units 39.

This heat exchanger 49 is constructed by stacking the above-described heat-exchanger tube array units 39 in plural layers. In this embodiment, the heat-exchanger tube array units are stacked in four layers. In the plural heat-exchanger tube array units 39 stacked in layers, the other ends of the primary branch tubes 21 are connected to a primary inlet header 51, one ends of the secondary branch tubes 25 are connected to a secondary inlet header 55, one ends of the primary collecting tubes 27 are connected to a primary outlet header 53, and the secondary collecting tubes 29 having one ends connected to a secondary outlet header 57. The number of stacked layers is not limited to four of the illustrated example, but may be more than this or less than this. It is preferred that the heat-exchanger tube array units are stacked in four to ten layers and have their respective collecting tubes and branch tubes connected to the respective headers.

The primary inlet header 51, the secondary inlet header 55, the primary outlet header 53 and the secondary outlet header 57 are each closed at one axial end thereof and each have a screwed fitting 59 fixed to the other axial end thereof. Tube fittings for a primary heat-medium supply piping, a secondary heat-medium supply piping, a primary heat-medium circulation piping and a secondary heat-medium circulation piping (not shown) extended from a heat exchanger apparatus each include, for example, a flared portion defined by an expanded tube end and a cap nut externally fitted on this flared portion.

With a sheet surface at an end of the screwed fitting 59 and the flared portion in intimate contact, an internal thread of the cap nut is threadably engaged with an external thread of the screwed fitting 59 so as to permit the heat exchanger 49 to be detachably mounted to the heat exchanger apparatus. The replacement of the heat exchanger 49 at maintenance work is facilitated by adopting this arrangement where the heat exchanger 49 is detachably mounted to the heat exchanger apparatus via the screwed fitting 59.

The primary inlet header 51, the secondary inlet header 55, the primary outlet header 53 and the secondary outlet header 57 are each closed at the end opposite from the end to which the screwed fitting 59 is fixed. The closed end is fixedly supported by a base plate 61, for example. It is noted that the primary inlet header 51, the secondary inlet header 55, the primary outlet header 53 and the secondary outlet header 57 may also have a tube fitting threadably engageable with the screwed fitting 59 fixed to the end opposite from the screwed fitting 59. Such a double-end joint structure permits another stack of plural layers of heat exchangers 49 to be stacked on the apparatus.

The heat exchanger tube 11 having such a configuration may be used to form the heat-exchanger tube array unit shown in FIG. 2 or FIG. 7 or to form the heat exchanger 49 shown in FIG. 18. Thus, a primary heat medium entering the primary inlet header 51 flows into the primary branch tube 21, from which the heat medium flows into the individual inner tubes 15. The primary heat medium flowing through the inner tubes 15 is subjected to heat exchange with a secondary heat medium and thereafter, enters the primary collecting tube 27 and flows out from the primary outlet header 53. The secondary heat medium entering the secondary inlet header 55 flows into the secondary branch tube 25, from which the heat medium flows into the outer tubes 13. The secondary heat medium flowing through the outer tubes 13 is subjected to heat exchange with the primary heat medium and thereafter, enters the secondary collecting tube 29 and flows out from the secondary outlet header 57.

The action of the heat exchanger 49 having the above structure is described.

In the heat exchanger 49, the heat medium in the inner tube 15 flows while contacting the heat transfer member 20 and the supporting member 19 disposed inside the inner tube 15, so that the contact area of the heat medium in the inner tube 15 is increased. The heat medium conventionally contacts only the inner-tube inner peripheral surface 38. The heat medium exchanges heat with the supporting member 19 and heat transfer member 20 through heat conduction effected by making contact with the supporting member 19 and heat transfer member 20. The exchanged heat is thermally conducted to the inner tube 15 so as to be subjected to heat exchange with a heat medium of another system which flows through the gap 31 between the outer tube 13 and the outer tube 15. Namely, the heat exchanged with the heat transfer member 20 and the supporting member 19 contributes to the improvement of heat exchange efficiency. This heat exchanger 49 is composed of a plurality of the heat exchanger tubes 11 each including the outer tube 13 and the inner tube 15, the heat exchanger tubes arranged on one plane in parallel and adjacent relation. The heat exchanger 49 formed on one plane can be stacked in plural layers as one unit or configured to reduce ground contact area while increasing the heat transfer area.

In addition to the above-described heat exchanger 49, the heat transfer tube 11 according to this embodiment can also form a cylindrical heat exchanger 65 as shown in FIG. 19 and FIG. 20.

This heat exchanger 65 is formed by bundling a plurality of heat exchanger tubes 11. The individual heat exchanger tubes 11 are supported at both ends thereof so as to be spaced a predetermined distance from one another and are housed in a cylindrical shell 67. According to this embodiment, as shown in FIG. 19, the heat exchanger includes a primary partition wall 69 and a secondary partition wall 73 which are shaped like a disk and include a plurality of support holes 71, 75 arranged in a matrix form or in rows and columns with equal spacing. The opposite ends of the heat transfer tubes are supported by these partition walls 69, 73 as penetrating therethrough. The primary partition wall 69 includes inner-tube support holes (primary support holes) 71 which have a hole diameter equal to the outside diameter of the inner tube 15 and are penetrated by the inner tubes 15. The secondary partition wall 73 includes outer-tube support holes (secondary support holes) 75 which have a hole diameter equal to the diameter of the outer tube 13 and are penetrated by the outer tubes 13. With the respective primary partition walls 69 penetrated by the tubes, a primary branch portion 79 is formed between the primary partition wall 69 at the inlet ends of the inner tubes 15 and an end wall 77 of the shell 67, while a primary collecting portion 81 is formed between the primary partition wall 69 at the outlet ends of the inner tubes 15 and the end wall 77 of the shell 67. A secondary branch portion 83 is formed between the primary partition wall 69 and the secondary partition wall 73 at the inlet ends of the outer tubes 13, while a secondary collecting portion 85 is formed between the primary partition wall 69 and the secondary partition wall 73 at the outlet ends of the outer tubes 13. In these heat exchanger tubes 11, connections between the outer tubes 13 and the secondary partition wall 73 and between the inner tubes 15 and the primary partition wall 69 are made by the above-described brazing. The gap support member 17 disposed in the gap between the outer tube 13 and the inner tube 15 is also fixed the same way. The ends of the outer tubes 13 and the ends of the inner tubes 15 open to the respective outsides of the partition walls 73, 69.

A plurality of straightening plates 87 are disposed in space between the opposite secondary partition walls 73, 73. These straightening plates 87 define planes perpendicular to the longitudinal direction of the heat exchanger tubes 11. Further, each of the straightening plates is configured to include a cut-away passage portion 89 such that the straightening plate in the shell 67 is partially out of contact with an inner periphery of the shell 67. For example, the straightening plate is shaped like a half-moon plate. The passage portions 89 of the straightening plates 87 are axially arranged in the shell 67 in a staggered fashion so as to define a tertiary flow passage meandering in a zigzag fashion in the shell 67. Each of the straightening plates 87 is formed with through-holes penetrated by and capable of supporting these heat exchanger tubes 11. Connections between these through-holes and the outer tubes 13 of the heat exchanger tubes 11 may preferably be fixed by the same brazing as described above.

At one end of the shell 67, as shown in FIG. 20, the primary branch portion 79 is provided with a primary inlet header 91; the secondary collecting portion 85 is provided with a secondary outlet header 93; and a tertiary inlet header 95 is provided as an inlet of the tertiary flow passage. At the other end of the shell 67, on the other hand, the primary collecting portion 81 is provided with a primary outlet header 97; the secondary branch portion 83 is provided with a secondary inlet header 99; and a tertiary outlet header 101 is provided as an outlet of the tertiary flow passage.

According to the heat exchanger 65 configured in this manner, the primary heat medium flowing through the primary inlet header 91 enters the primary branch portion 79, from which the heat medium flows into the individual inner tubes 15. The primary heat medium flowing through the inner tubes 15 is subjected to heat exchange with the secondary heat medium. Subsequently, the heat medium flows into the primary collecting portion 81 and flows out from the primary outlet header 97. The secondary heat medium flowing through the secondary inlet leader 99 enters the secondary branch portion 83, from which the heat medium flows into the outer tubes 13. The secondary heat medium flowing through the outer tubes 13 is subjected to heat exchange with the primary heat medium. Subsequently, the heat medium flows into the secondary collecting portion 85 and flows out from the secondary outlet header 93. A tertiary heat medium flowing through the tertiary inlet header 95 enters the shell 67 and flows around the outer tubes 13 as made to meander by the individual straightening plates 87. The tertiary heat medium flowing through the shell 67 is subjected to heat exchange with the secondary heat medium. Subsequently, the heat medium flows out from the tertiary outlet header 101. It is noted that the tertiary heat medium may be the same as the primary heat medium.

In this heat exchanger 65, the heat exchanger tubes 11 are capable of heat exchange with the tertiary heat medium in the shell 67. Therefore, the ratio S1:S2 between the area S1 of the primary flow passage in the inner tube 15 and the area S2 of the secondary flow passage in the outer tube 13 can be set to the range of 1:4 to 1:2. Hence, the wire diameters of the gap support member 17 located in the gap between the outer tube 13 and the inner tube 15 and of the supporting member 19 in the inner tube 15, the configuration and sectional area of the heat transfer member 20 can also be increased or decreased as needed according to these ratios.

Therefore, the heat exchanger tube 11 and the heat exchanger 49 according to the embodiments of the invention can increase the efficiency of heat exchange between the inner tube 15 and the heat medium flowing therethrough.

REFERENCE SIGNS LIST

-   11 . . . HEAT EXCHANGER TUBE -   13 . . . OUTER TUBE -   15 . . . INNER TUBE -   17, 45 . . . GAP SUPPORT MEMBER -   19 . . . SUPPORTING MEMBER -   20 . . . HEAT TRANSFER MEMBER -   21 . . . PRIMARY BRANCH TUBE -   25 . . . SECONDARY BRANCH TUBE -   27 . . . PRIMARY COLLECTING TUBE -   29 . . . SECONDARY COLLECTING TUBE -   30 . . . INNER-TUBE OUTER PERIPHERAL SURFACE -   31 . . . GAP -   32 . . . OUTER-TUBE INNER PERIPHERAL SURFACE -   38 . . . INNER-TUBE INNER PERIPHERAL SURFACE -   41 . . . LARGE DIAMETER PORTION -   43 . . . SMALL DIAMETER PORTION -   49, 65 . . . HEAT EXCHANGER -   67 . . . SHELL -   87 . . . STRAIGHTENING PLATE -   141 . . . SHEET -   153 . . . OUTER-PERIPHERY PROTRUDING ROUND ROD -   155 . . . OVAL PORTION -   157 . . . LARGE DIAMETER PORTION -   159 . . . SMALL DIAMETER PORTION -   161 . . . DIFFERENT-DIAMETER ROUND ROD -   165 . . . SOLID ROD -   d1 . . . WIRE DIAMETER OF GAP SUPPORT MEMBER -   D1 . . . COIL INSIDE DIAMETER -   D2 . . . COIL OUTSIDE DIAMETER -   D4 . . . INSIDE DIAMETER OF OUTER TUBE -   D5 . . . OUTSIDE DIAMETER OF INNER TUBE -   W . . . GAP 

1. A heat exchanger tube comprising: an outer tube; an inner tube inserted in the outer tube; a gap support member including a wire material which is disposed in a gap between an inner periphery of the outer tube and an outer periphery of the inner tube, and makes spiral contact with the inner periphery and the outer periphery substantially throughout the length of the outer tube; and a supporting member including a wire material which makes spiral contact with an inner periphery of the inner tube throughout the length of the inner tube.
 2. The heat exchanger tube according to claim 1, wherein the gap support member comprises a coil material and has a wire diameter substantially equal to the gap.
 3. The heat exchanger tube according to claim 1, wherein the gap support member comprises a coil material having a small diameter portion and a large diameter portion alternately formed, and has a wire diameter smaller than the gap, a coil inside diameter at the small diameter portion defined by an outside diameter of the inner tube, and a coil outside diameter at the large diameter portion defined by an inside diameter of the outer tube, thus supporting the inner tube in the outer tube.
 4. A heat exchanger tube comprising: an outer tube; an inner tube inserted in the outer tube; a gap support member including a wire material which is disposed in a gap between an outer-tube inner peripheral surface and an inner-tube outer peripheral surface, and makes spiral contact with the outer-tube inner peripheral surface and the inner-tube outer peripheral surface substantially throughout the length of the outer tube; a supporting member including a wire material which makes spiral contact with the inner-tube inner peripheral surface throughout the length of the inner tube; and a heat transfer member which is extended centrally through the supporting member throughout the length of the supporting member and at least a part of the outer periphery of the heat transfer member is in contact with the supporting member.
 5. The heat exchanger tube according to claim 4, wherein the heat transfer member is a sheet elongated in a longitudinal direction of the supporting member and twisted spirally.
 6. The heat exchanger tube according to claim 4, wherein the heat transfer member is an outer-periphery protruding round rod including oval portions made by deforming a round outer periphery thereof at predetermined space intervals in the longitudinal direction of the supporting member.
 7. The heat exchanger tube according to claim 4, wherein the heat transfer member is a different-diameter round rod with its round outer periphery alternately formed of a small diameter portion and a large diameter portion at predetermined space intervals in the longitudinal direction of the supporting member.
 8. The heat exchanger tube according to claim 4, wherein the heat transfer member is a solid rod having a polygonal cross section.
 9. A heat exchanger employing the heat exchanger tube according to claim 1, wherein a plurality of the heat exchanger tubes are arranged in mutually parallel relation, a primary flow passage is formed by connecting all the inner-tube inlet ends to a primary branch tube and connecting all the inner-tube outlet ends to a primary collecting tube, and a secondary flow passage is formed by connecting all the outer-tube inlet ends to a secondary branch tube and connecting all the outer-tube outlet ends to a secondary collecting tube.
 10. A heat exchanger employing the heat exchanger tube according to claim 1, wherein the plurality of heat exchanger tubes are bundled, the bundle of heat exchanger tubes is housed in a cylindrical shell, a primary flow passage is formed by interconnecting inlet ends of the inner tubes and interconnecting outlet ends of the inner tubes, a secondary flow passage is formed by interconnecting inlet ends of the outer tubes and interconnecting outlet ends of the outer tubes, and an interior of the shell is configured as a tertiary flow passage.
 11. The heat exchanger according to claim 10, wherein a plurality of straightening plates having planes perpendicular to a longitudinal direction of the heat exchanger tubes are disposed in the shell so as to support the heat exchanger tubes and to make the tertiary flow passage meander. 